The invention relates to continuously variable transmission mechanisms.
It has already been proposed in U.K. Patent Specification 1,153,572 to provide a continuously variable transmission mechanism including a roller assembly comprising first and second rollers separately mounted in spaced relation for rotation about a first axis, a disc assembly comprising first and second discs mounted on a disc carrier in spaced relation for rotation about one or more second axes transverse to the first axis and so that the peripheries of the rollers engage inwardly facing surfaces of the discs with the or each second axis located between the rollers. In this transmission means are also provided for urging the discs towards the first axis into frictional driving engagement with the roller peripheries. The means for urging the discs towards the first axis incorporates a spindle extending through the whole assembly and carrying the discs and is made responsive to the torque actually being transmitted by the transmission by making it responsive to the torque reaction which holds the disc carrier against rotation. The spindle extending through the centre of the assembly between the discs is loaded in tension to transmit the forces urging the discs towards the first axis between the two discs. The ratio of the transmission is varied by causing relative movement between the roller assembly and the disc assembly in a direction parallel to the first axis to vary the effective diameters on the discs which are engaged by the rollers.
The torque and power which can be transmitted by such a transmission mechanism is limited due to the limitations of the rolling friction drive and it would be desirable to be able to provide a similar compact and relatively simple transmission mechanism capable of transmitting greater power and torque, and to vary the range of ratios which can be transmitted.